Ram Install

I have a PowerEdge 2900 iii with SBS 2008 and i just bought some Crucial ram (2 sticks of 4GB memory). My server is running with only 4GB of ram and i noticed that 90% is in use (my guess is this is from using exchange server also).

I currently have 4 sticks of 1GB memory in the server, and 8 open slots.

I wanted to know if there was any certain order i should put the ram in (should i move the 1GB down and put the new larger sticks in it place)? Also, is there any downside of using 2 sticks of 4GB with 4 sticks of 1GB ram?

You definitely don't want to simply "... put the additional RAM in the spare slots ...". Performance can be very adversely affected if you don't ensure the optimal quad-channel arrangment (two dual-channel

1: Make sure you are using a 64 bit operating system since over 4GB of RAM can crash a 32 bit OS.
2: There is no specific order in which you may put in RAM, just be sure to get it into two paired slots ( to take advantage of the speed benefits of doing so. ).

You definitely don't want to simply "... put the additional RAM in the spare slots ...". Performance can be very adversely affected if you don't ensure the optimal quad-channel arrangment (two dual-channel branches). The alignment of the slots by channel and branch is shown on page 83 of the hardware manual: http://support.dell.com/support/edocs/systems/pe2900/en/hom/pdf/hom.pdf

Note that Dell says you must install either 2, 4, 8, or 12 modules ... so it's not clear what will happen if you install a total of 6 modules (won't hurt to try it). I suspect the memory will be "seen", but the performance will suffer because the system doesn't have matched modules in the two branches (so effectively you'll slow down from quad-channel access to dual-channel access) => but it depends on how the BIOS treats that arrangement. Assuming it works okay (and you "see" 12GB), I suspect you'll get a warning message on startup about "non-optimal" memory configuration.

If you want to try it, install the two new modules in slots 5 and 6 (your current modules should be in 1, 2, 3, and 4). But I'd follow Dell's instructions and install 4 more modules rather than just 2.

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You need to determine if the modules are one Rank or two Rank.
That might come into play with the slot arrangement.

I have a similar board (only Intel) and the previously suggested slot arrangement isn't a good idea.
- See drawing from your manual...
The correct arrangement would seem to be:
1GB in slots 1,5,2,6
4GB in slots 3,4
That keeps the channels and branches as balanced as you can do with what you have.
Hopefully the 1Gb is 1R and the 4GB is 2R.

I agree that you be better off getting two more 4GB modules and discarding the 1GB.
[Or sell, use in something else, whatever,,,,]

As I noted before, it depends on how the BIOS configures the memory access with 6 installed memory modules => since Dell says to only install 2, 4, 8, or 12 modules, that situation isn't addressed in the documentation.

If you "see" 12GB, then the question is what mode is it accessing it in. Run CPU-Z [http://www.cpuid.com/cpuz.php ] and look on the memory tab to see what the current mode is.

You might then want to try the two configurations you asked about above and see which mode each of them use. I'd expect that either will run just fine, since both are within the Dell-specified configurations (although the 4 1GB modules may run at a higher speed, since it should be accessed in quad-channel mode).

I would try the 4 1GB with the 2 4GB sticks and if it doesn't work switch to just the two 4GB modules.
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That would be a valid configuration in the board I have.
Biggest difference between your and my boards for RAM is that mine only has two slots per channel.
I'm missing your slots 9, 10, 11, 12.

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